The present invention relates to a detector for detecting the level of stored liquid and, more particularly, to an ink level detector for use with an ink jet printer.
A prior art ink level detector used with an ink jet printer comprises two spaced rod-like electrodes which extend downwardly from an upper wall of an ink reservoir. Ink is supplied from an ink cartridge into the ink reservoir in which the two electrodes are positioned. When the ink in the reservoir has been consumed to such an extent that one of the electrodes does not make contact with the ink at all, that is, the electrode is clear of the ink surface, the detector determines that a "no ink" condition has been reached. Specifically, in the prior art ink level detector, the two electrodes are dipped in the ink in the reservoir to detect an ink level in terms of electrical resistance therebetween.
In such a prior art ink level detector, the electrodes are located in a position remote from the ink cartridge which is mounted on the ink reservoir and this brings about a problem. That is, once the ink level fluctuates due to movement of the ink inside the reservoir or the printer and, therefore, the reservoir is tilted, the electrodes are apt to sense the ink at a false level, resulting in scattering in level detection. Meanwhile, as regards a certain kind of ink jet printer, the viscosity of ink increases as it is repeatedly circulated and such has heretofore been compensated for by discarding a predetermined amount of ink. This brings about another problem that since no fresh ink is supplemented after the ink cartridge has been emptied, the viscosity sharply increases to affect the quality of data to be printed out.